42 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



Steam, moisture and drought, mice, worms, slugs, aphides, and 

 insects innumerable, as Cowper says, oft work dire disappoint- 

 ment, that admits no cure, and which no care can obviate. It 

 is, therefore, the more requisite that the structure intended for 

 these purposes should be the best that science and practice can 

 adopt. 



Fig. 5 is the end section of a forcing-stove, which we have 

 seen used in various parts of this country, with considerable suc- 

 cess. It is sunk a few feet into the ground, so that the roof 

 reaches within about two feet of the ground level. In some 

 places this kind of pit answers very well, as in very dry and 

 sheltered situations. The site of such a pit must necessarily be 

 in gravel, or sand ; in wet clay, coldness and dampness would be 

 unavoidable ; and in exposed situations, it would be very unsuit- 

 able for winter forcing, unless provision were made for covering 

 it at night. 



Fig. 5. 



Fig, 6 shows the end section of a polyprosopic forcing-house, 

 which, by some, is considered superior to all other forms for 

 winter forcing. The roof presents the different faces to the sun's 

 rays, <z, a, «, at different periods of the year. This kind of roof 

 may be considered as exactly equivalent to a curvilinear figure, 

 whose curved lines shall touch all the angles of the faces, so that, 

 were the house built in the form of a semi-ellipse, or having 

 curved ends, the sun would be nearly perpendicular to some one 

 of the faces every hour of the day, and every day in the year. 



The rafters in this house are curved the same as in a cunri- 



